2026 Volume 68 Pages 22-28
In Shizuoka Prefecture, increased production of tencha—the raw material for matcha, whose exports are rising—has lead to expanded shaded tea cultivation, including in mountainous and hilly regions. However, tea blister blight disease has become an increasing problem in these areas, creating a need for effective control measures that also minimize pesticide residue. Accordingly, this study evaluated the effects of direct cover application and copper fungicide spraying on the incidence of blister blight. Field trials combining cover application and copper fungicide spraying were conducted at the Tea Research Center, Shizuoka Prefectural Research Institute of Agriculture and Forestry (Kikugawa City, Shizuoka Prefecture) and at a local organic tea plantation (Kawane Town, Shimada City, Shizuoka Prefecture). Disease incidence was assessed under each treatment condition. In a 2022 trial, cover application increased the number of blister blight-infected leaves. In contrast, no difference in disease incidence between covered and uncovered plots was observed in 2023, suggesting that the effect of cover application on blister blight may depend on prevailing weather conditions. In both years, copper fungicide application before or during sprouting reduced the number of infecetd leaves, although the magnitude of this effect also varied with weather conditions.
